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Dust mites: Just the Facts!

Dust mites were first discovered in house dust in 1694. Dust mites belong to the Family Arachnids similar to spiders and ticks and therefore they have 8 legs.  There are 2 main species (Dermataphagoides farinae  is the American House Dust mite and D. pteronyssinus the European House Dust Mite).  However, they can both be found on all continents.  They are microscopic (not visible with the naked eye).  They are blind and do not bite.  They feed on human skin scales (dandruff) and absorb water from the air rather than drink it.  They live in carpet, upholstered furniture, pillows, mattresses and stuffed animals.  They grow particularly well in warm (77 to 86 degrees F) and moist environments (relative humidity 75%).  The higher the altitude, the less dust mites are found. A dust mite defecates about 20 large fecal balls daily. This fecal pellet contains protein digestive enzymes and when inhaled into the nose or lungs can be responsible for triggering year-round allergies (perennial allergic rhinitis) and asthma respectively.   These fecal pellets have also been documented as a trigger for worsening atopic dermatitis (allergic eczema).

An allergist can apply a standardized skin test for house dust mite and in 20 minutes determine if you are allergic to them.  If so, there are several practical measures to take to decrease your exposure to dust mites.   By doing so, you could experience less allergy and asthma symptoms and require less medication.

To decrease your exposure to dust mites, follow these recommendations:

  • Place mite-proof fabric encasements over the pillow, mattress and box springs.  The weave on the material is so tight it allows air to flow through, but not dust mite allergen.   Reputable dust mite cover manufacturers include:
    • Allergy Guardian - http://www.allergyguardian.com/ - (800) 631-3549
    • National Allergy - http://www.natlallergy.com/ - (800) 522-1448
    • Allergy Control Products - http://www.allergycontrol.com/ - (800) 255.3749
    • Mission Allergy - http://www.missionallergy.com/home.asp - (877) 662-5537
  • Plastic covers feel, well, like plastic.  They can make you sweat, are noisy and uncomfortable. Synthetic pillows are no better than feather pillows according to research published by Mills, S. in the New Zealand Medical Journal in 2002.

  • Do not purchase covers from the department store, as they do not often cover all sides the entire mattress or component of the bed.  Many manufacturers claim to be "allergen-proof" but are not.
  • Keep the relative humidity in the house below 45 to 50%; do not run humidifiers or vaporizers for prolonged periods of time as this could increase the humidity and promote mite growth.

  • Remove carpets and replace with wipeable floors (wood, tile, linoleum, vinyl, laminate).  Throw rugs can be washed in hot water every 2 weeks.

  • If carpets cannot be removed, vacuum once a week (have your non-allergic spouse do the vacuuming).  Dry steam cleaning followed by weekly vacuuming can reduce carpet levels of dust mite allergen longer (up to 8 weeks).  Use a high quality vacuum cleaner that traps the dust in a HEPA filter and doesn’t allow it to escape.

  • Steam clean or vacuum upholstered furniture.  If possible obtain leather, wood or plastic furniture that can be wiped down quickly and easily.

  • When dusting, use a multi-surface duster that traps dust, rather than a spray can that propels dust making it airborne.

  • Replace draperies with blinds that can be dusted easily.

  • Wash bedding (sheets, pillow case, blankets) every 1-2 weeks in HOT water (over 127-135o F).  This high temperature will kill dust mites.   This temperature is higher than the recommended 120o by the American Academy of Pediatrics to prevent scald burns.  Therefore after you wash the bedding in HOT water, turn the hot water heater back down.  If you decide to use warm water, do a long pre-soak and add bleach.

What doesn’t work so well:

  • Room air cleaners.  Dust mite allergen is heavy and does not stay airborne for long periods of time like animal dander, smoke or mold spores.  Dust mite allergen will settle back down into the carpet and onto other surfaces after it has been disturbed.  Also, avoid ozone generating air cleaners, as these are unsafe for individuals with asthma and other lung problems.

  • Putting the stuffed animals in the freezer may kill the dust mite, but it doesn’t break down the fecal pellet that is the cause of the symptoms.

  • Duct cleaning may remove a lot of things you don’t want in your ducts, but studies have shown little effect on heat duct cleaning specifically for dust mites.
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